Perhaps you should try some spelling variations:
khanh dai » thanh dat, khanh van, phan dai
te sach » toc sach
duoc xa » duoc ma, duoc va, duoc ha
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va, hieu qua
tu cong » thu cong, te cong, tai cong
tu nong » tu dong, tu tong, tu tuong
duc xa » tuc xa, duc va, duc ha
va cao » va cac, va co, va dao

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ((tu nong) or (tu cong)) xa hoi. hieu va cao ((duc xa) OR (duoc xa)) khanh dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ((tu nong) OR (tu cong)) xa hoi. hieu va cao ((duc xa) OR (duoc xa)) khanh dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ((tu nong) or (tu cong)) xa hoi. hieu va cao ((duc xa) OR (duoc xa)) khanh dai cua tre".
• Adding a wildcard symbol may retrieve word variants: te sach ((tu nong) or (tu cong)) xa hoi. hieu va cao ((duc xa) OR (duoc xa)) khanh dai cua tre*.